Bone grafting refers to a wide variety of medical and dental surgical procedures by which the formation of new bone in a patient is augmented or stimulated. Bone grafting is used in many types of orthopedic procedures to treat bone fractures or loss, to repair injured bone that has not healed, and to fuse together joints to prevent movement. With particular reference to the spine, grafts have been used to stabilize the spine and to prevent movement by selected vertebral segments, which may be a significant cause of pain in some patients. Grafts have also been used to correct or stop the progress of spinal deformity, such as scoliosis, and to provide structural support for fractures of the spine.
Suitable grafts can be harvested from bones in the patient's own body (autografts), from bones in members of the same species (allograft), and from bones in members of other animal species (xenograft). Alternatively, bone grafts can be created from a wide variety of natural and/or synthetic materials, such as collagen, polymers, hydroxyapatite, calcium sulfate, ceramics, and bioresorbable polymers, among many others. It is understood that bone grafts can include those which have a predetermined shaped or which are comprised of smaller particles that can be formed into a desired shape at the time of implantation.
Regardless of the source, bone grafts must be adequately preserved for later implantation in a surgical setting. One common practice is to dehydrate the grafts by freeze-drying. This not only extends the shelf-life of the bone grafts, it also inhibits bacterial growth within the graft. Before implanting the graft into a recipient, however, the graft must be reconstituted or rehydrated with a suitable liquid. This can be done by immersing the bone graft in the liquid. The problem with this approach, however, is that infusion of the liquid through the pores of the graft is typically unacceptably slow for a surgical environment and does not ensure thorough and complete infusion of the liquid throughout the graft. Moreover, this approach increases the likelihood of exposing the graft to environmental pathogens.
Another significant challenge in preparing grafts for implantation is the uniform loading or seeding of grafts with desired biological components and cells. Developing functional tissue equivalents requires the effective and uniform seeding of biological components and cells into natural or synthetic matrices and allowing them to expand and develop into the tissue-like structure from the seeded cells. Thus, the ability to efficiently and uniformly seed biological components and cells into three-dimensional scaffolds remains a significant aspect in tissue engineering.